This invention relates to sequence control systems and more particularly to an improved system which is programmable to control both the sequence of a set of operations to be performed and the time allotted for performance of each operation.
In many manufacturing operations in which a machine performs a series of operations automatically, it is desirable to monitor the operation of the machine and to control it to ensure that an operation may be initiated only if a preceding operation has been satisfactorily completed. Typical, known arrangements for controlling a sequence of steps or operations involve the use of electronic shift registers or ring counters and are limited in the scope of their monitoring function. The arrangements which do perform a monitoring function may be quite complex and often involve the use of programmed computers which require skilled operators to use and to maintain.